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Bathtub installation question

I'm installing a new soaker-style bathtub as part of a bathroom renovation.  It is acrylic, and is designed to fit into a cutout.  That is, there is a tiled space between the lip of the tub and the tiled walls around the tub.

I bought the tub on sale as a demo model from a home store (Rona, kinda like Home Depot), and as such it came with no installation instructions.  I couldn't find them online, and I wasn't able to get any help from the manufacturer, either.  Perhaps I need to pester them more.

Anyway, the issue is this.  On many similar tub installs, I've seen them layer up mortar under the tub for support.  However, my tub has two wooden rails (2x3s) permanently fiberglassed to the bottom.  In addition, a very dense hardboard spans the entire bottom of the tub.  It really seems as if the tub is designed to be set on the floor just like that, perhaps with wood blocks screwed in around the edges of the rails to keep the tub from shifting.

I can do that if that's how it should be done.  I just don't want to risk cracking the tub with hundreds of pounds of water and human - my wife would not be pleased, nor would I.  Does anyone have experience with this sort of thing?

aeray6 years ago
The way it is done in my area of the US is to install temporary blocks (equal to the thickness of the thinset mortar and tile you will be using) between the top of the tub deck and the bottom of the tub rim. The bottom of the tub should be an inch or so above the subfloor. Make damn sure that the drain lines up with plumbing, and make a few reference marks to ensure this alignment later. Make a pile of thinset mortar, or my favorite, expansion foam, about 2-3 inches deep where the bottom of the tub will be. Place a piece of plastic sheeting over the pile (VERY important) and set the tub into place, pushing and wiggling it to seat it against the temporary blocks, checking against your reference marks. Let the mortar or foam cure.

Remove the tub (that the plastic kept from sticking) and tile the surround. If the tub has a pump or heater remember to plan for and install an access hatch should things need to be repaired.

When you're done tiling and grouting, reset the tub. Check the plumbing alignment and measure the length of tailpiece you'll need. Pull the tub back out. Attach the supply lines and fittings. Attach the drain and tailpiece to the tub and let the glue dry. Reset the tub the final time after applying glue to the tailpiece and plumbing. If you're lucky, the access hatch will be helpful for this. Caulk the tub rim to the tile, and let everything sit for at least a day, then fill it about halfway and leave it over night to check for leaks.

I like to use foam because it is easier, quieter, and insulating. Deck-set rim-mounted tubs are a pain in the butt.

Good luck!
That's a fairly common way to find a European tub supplied - ours came with thin 1" square steel tubes rails, and jacking screws to level it. 2 x 3 sounds stronger to me. Don't forget to set the tub seals finally filled with water.
jeff-o (author)  steveastrouk6 years ago
So then it sits right on the rails, then? Easy then. I'm not sure what you mean in the last sentence...
Its important to make sure the tub is seated down nicely on its feet. Fill it to the overflow, and leave it overnight to settle before you run any sealant round the edges, or try and set tile.

Steve